pub fn encryption(input: String) -> String {
    // S-boxes
    const S0: [u8; 256] = [
        0x3e, 0x72, 0x5b, 0x47, 0xca, 0xe0, 0x00, 0x33, 0x04, 0xd1, 0x54, 0x98, 0x09, 0xb9, 0x6d,
        0xcb, 0x7b, 0x1b, 0xf9, 0x32, 0xaf, 0x9d, 0x6a, 0xa5, 0xb8, 0x2d, 0xfc, 0x1d, 0x08, 0x53,
        0x03, 0x90, 0x4d, 0x4e, 0x84, 0x99, 0xe4, 0xce, 0xd9, 0x91, 0xdd, 0xb6, 0x85, 0x48, 0x8b,
        0x29, 0x6e, 0xac, 0xcd, 0xc1, 0xf8, 0x1e, 0x73, 0x43, 0x69, 0xc6, 0xb5, 0xbd, 0xfd, 0x39,
        0x63, 0x20, 0xd4, 0x38, 0x76, 0x7d, 0xb2, 0xa7, 0xcf, 0xed, 0x57, 0xc5, 0xf3, 0x2c, 0xbb,
        0x14, 0x21, 0x06, 0x55, 0x9b, 0xe3, 0xef, 0x5e, 0x31, 0x4f, 0x7f, 0x5a, 0xa4, 0x0d, 0x82,
        0x51, 0x49, 0x5f, 0xba, 0x58, 0x1c, 0x4a, 0x16, 0xd5, 0x17, 0xa8, 0x92, 0x24, 0x1f, 0x8c,
        0xff, 0xd8, 0xae, 0x2e, 0x01, 0xd3, 0xad, 0x3b, 0x4b, 0xda, 0x46, 0xeb, 0xc9, 0xde, 0x9a,
        0x8f, 0x87, 0xd7, 0x3a, 0x80, 0x6f, 0x2f, 0xc8, 0xb1, 0xb4, 0x37, 0xf7, 0x0a, 0x22, 0x13,
        0x28, 0x7c, 0xcc, 0x3c, 0x89, 0xc7, 0xc3, 0x96, 0x56, 0x07, 0xbf, 0x7e, 0xf0, 0x0b, 0x2b,
        0x97, 0x52, 0x35, 0x41, 0x79, 0x61, 0xa6, 0x4c, 0x10, 0xfe, 0xbc, 0x26, 0x95, 0x88, 0x8a,
        0xb0, 0xa3, 0xfb, 0xc0, 0x18, 0x94, 0xf2, 0xe1, 0xe5, 0xe9, 0x5d, 0xd0, 0xdc, 0x11, 0x66,
        0x64, 0x5c, 0xec, 0x59, 0x42, 0x75, 0x12, 0xf5, 0x74, 0x9c, 0xaa, 0x23, 0x0e, 0x86, 0xab,
        0xbe, 0x2a, 0x02, 0xe7, 0x67, 0xe6, 0x44, 0xa2, 0x6c, 0xc2, 0x93, 0x9f, 0xf1, 0xf6, 0xfa,
        0x36, 0xd2, 0x50, 0x68, 0x9e, 0x62, 0x71, 0x15, 0x3d, 0xd6, 0x40, 0xc4, 0xe2, 0x0f, 0x8e,
        0x83, 0x77, 0x6b, 0x25, 0x05, 0x3f, 0x0c, 0x30, 0xea, 0x70, 0xb7, 0xa1, 0xe8, 0xa9, 0x65,
        0x8d, 0x27, 0x1a, 0xdb, 0x81, 0xb3, 0xa0, 0xf4, 0x45, 0x7a, 0x19, 0xdf, 0xee, 0x78, 0x34,
        0x60,
    ];

    const S1: [u8; 256] = [
        0x55, 0xc2, 0x63, 0x71, 0x3b, 0xc8, 0x47, 0x86, 0x9f, 0x3c, 0xda, 0x5b, 0x29, 0xaa, 0xfd,
        0x77, 0x8c, 0xc5, 0x94, 0x0c, 0xa6, 0x1a, 0x13, 0x00, 0xe3, 0xa8, 0x16, 0x72, 0x40, 0xf9,
        0xf8, 0x42, 0x44, 0x26, 0x68, 0x96, 0x81, 0xd9, 0x45, 0x3e, 0x10, 0x76, 0xc6, 0xa7, 0x8b,
        0x39, 0x43, 0xe1, 0x3a, 0xb5, 0x56, 0x2a, 0xc0, 0x6d, 0xb3, 0x05, 0x22, 0x66, 0xbf, 0xdc,
        0x0b, 0xfa, 0x62, 0x48, 0xdd, 0x20, 0x11, 0x06, 0x36, 0xc9, 0xc1, 0xcf, 0xf6, 0x27, 0x52,
        0xbb, 0x69, 0xf5, 0xd4, 0x87, 0x7f, 0x84, 0x4c, 0xd2, 0x9c, 0x57, 0xa4, 0xbc, 0x4f, 0x9a,
        0xdf, 0xfe, 0xd6, 0x8d, 0x7a, 0xeb, 0x2b, 0x53, 0xd8, 0x5c, 0xa1, 0x14, 0x17, 0xfb, 0x23,
        0xd5, 0x7d, 0x30, 0x67, 0x73, 0x08, 0x09, 0xee, 0xb7, 0x70, 0x3f, 0x61, 0xb2, 0x19, 0x8e,
        0x4e, 0xe5, 0x4b, 0x93, 0x8f, 0x5d, 0xdb, 0xa9, 0xad, 0xf1, 0xae, 0x2e, 0xcb, 0x0d, 0xfc,
        0xf4, 0x2d, 0x46, 0x6e, 0x1d, 0x97, 0xe8, 0xd1, 0xe9, 0x4d, 0x37, 0xa5, 0x75, 0x5e, 0x83,
        0x9e, 0xab, 0x82, 0x9d, 0xb9, 0x1c, 0xe0, 0xcd, 0x49, 0x89, 0x01, 0xb6, 0xbd, 0x58, 0x24,
        0xa2, 0x5f, 0x38, 0x78, 0x99, 0x15, 0x90, 0x50, 0xb8, 0x95, 0xe4, 0xd0, 0x91, 0xc7, 0xce,
        0xed, 0x0f, 0xb4, 0x6f, 0xa0, 0xcc, 0xf0, 0x02, 0x4a, 0x79, 0xc3, 0xde, 0xa3, 0xef, 0xea,
        0x51, 0xe6, 0x6b, 0x18, 0xec, 0x1b, 0x2c, 0x80, 0xf7, 0x74, 0xe7, 0xff, 0x21, 0x5a, 0x6a,
        0x54, 0x1e, 0x41, 0x31, 0x92, 0x35, 0xc4, 0x33, 0x07, 0x0a, 0xba, 0x7e, 0x0e, 0x34, 0x88,
        0xb1, 0x98, 0x7c, 0xf3, 0x3d, 0x60, 0x6c, 0x7b, 0xca, 0xd3, 0x1f, 0x32, 0x65, 0x04, 0x28,
        0x64, 0xbe, 0x85, 0x9b, 0x2f, 0x59, 0x8a, 0xd7, 0xb0, 0x25, 0xac, 0xaf, 0x12, 0x03, 0xe2,
        0xf2,
    ];

    const EK_D: [u32; 16] = [
        0x44D7, 0x26BC, 0x626B, 0x135E, 0x5789, 0x35E2, 0x7135, 0x09AF, 0x4D78, 0x2F13, 0x6BC4,
        0x1AF1, 0x5E26, 0x3C4D, 0x789A, 0x47AC,
    ];

    fn add_m(a: u32, b: u32) -> u32 {
        let c = a.wrapping_add(b);
        (c & 0x7FFF_FFFF).wrapping_add(c >> 31)
    }

    fn mul_by_pow2(x: u32, k: u32) -> u32 {
        ((x << k) | (x >> (31 - k))) & 0x7FFF_FFFF
    }

    struct ZucState {
        lfsr_s: [u32; 16],
        f_r1: u32,
        f_r2: u32,
        brc_x: [u32; 4],
    }

    impl ZucState {
        fn new() -> Self {
            ZucState {
                lfsr_s: [0; 16],
                f_r1: 0,
                f_r2: 0,
                brc_x: [0; 4],
            }
        }

        fn lfsr_with_initialization_mode(&mut self, u: u32) {
            let mut f = self.lfsr_s[0];
            f = add_m(f, mul_by_pow2(self.lfsr_s[0], 8));
            f = add_m(f, mul_by_pow2(self.lfsr_s[4], 20));
            f = add_m(f, mul_by_pow2(self.lfsr_s[10], 21));
            f = add_m(f, mul_by_pow2(self.lfsr_s[13], 17));
            f = add_m(f, mul_by_pow2(self.lfsr_s[15], 15));
            f = add_m(f, u);

            for i in 0..15 {
                self.lfsr_s[i] = self.lfsr_s[i + 1];
            }
            self.lfsr_s[15] = f;
        }

        fn lfsr_with_work_mode(&mut self) {
            let mut f = self.lfsr_s[0];
            f = add_m(f, mul_by_pow2(self.lfsr_s[0], 8));
            f = add_m(f, mul_by_pow2(self.lfsr_s[4], 20));
            f = add_m(f, mul_by_pow2(self.lfsr_s[10], 21));
            f = add_m(f, mul_by_pow2(self.lfsr_s[13], 17));
            f = add_m(f, mul_by_pow2(self.lfsr_s[15], 15));

            for i in 0..15 {
                self.lfsr_s[i] = self.lfsr_s[i + 1];
            }
            self.lfsr_s[15] = f;
        }

        fn bit_reorganization(&mut self) {
            self.brc_x[0] = ((self.lfsr_s[15] & 0x7FFF8000) << 1) | (self.lfsr_s[14] & 0xFFFF);
            self.brc_x[1] = ((self.lfsr_s[11] & 0xFFFF) << 16) | (self.lfsr_s[9] >> 15);
            self.brc_x[2] = ((self.lfsr_s[7] & 0xFFFF) << 16) | (self.lfsr_s[5] >> 15);
            self.brc_x[3] = ((self.lfsr_s[2] & 0xFFFF) << 16) | (self.lfsr_s[0] >> 15);
        }

        fn l1(x: u32) -> u32 {
            x ^ x.rotate_left(2) ^ x.rotate_left(10) ^ x.rotate_left(18) ^ x.rotate_left(24)
        }

        fn l2(x: u32) -> u32 {
            x ^ x.rotate_left(8) ^ x.rotate_left(14) ^ x.rotate_left(22) ^ x.rotate_left(30)
        }

        fn f(&mut self) -> u32 {
            let w = (self.brc_x[0] ^ self.f_r1).wrapping_add(self.f_r2);
            let w1 = self.f_r1.wrapping_add(self.brc_x[1]);
            let w2 = self.f_r2 ^ self.brc_x[2];

            let u = Self::l1((w1 << 16) | (w2 >> 16));
            let v = Self::l2((w2 << 16) | (w1 >> 16));

            self.f_r1 = ((S0[(u >> 24) as usize] as u32) << 24)
                | ((S1[((u >> 16) & 0xFF) as usize] as u32) << 16)
                | ((S0[((u >> 8) & 0xFF) as usize] as u32) << 8)
                | (S1[(u & 0xFF) as usize] as u32);

            self.f_r2 = ((S0[(v >> 24) as usize] as u32) << 24)
                | ((S1[((v >> 16) & 0xFF) as usize] as u32) << 16)
                | ((S0[((v >> 8) & 0xFF) as usize] as u32) << 8)
                | (S1[(v & 0xFF) as usize] as u32);

            w
        }

        fn initialization(&mut self, k: &[u8], iv: &[u8]) {
            for i in 0..16 {
                self.lfsr_s[i] = ((k[i] as u32) << 23) | ((EK_D[i] as u32) << 8) | (iv[i] as u32);
            }

            self.f_r1 = 0;
            self.f_r2 = 0;

            for _ in 0..32 {
                self.bit_reorganization();
                let w = self.f();
                self.lfsr_with_initialization_mode(w >> 1);
            }

            self.bit_reorganization();
            self.f();
            self.lfsr_with_work_mode();
        }

        fn generate_keystream(&mut self, len: usize) -> Vec<u32> {
            let mut keystream = Vec::with_capacity(len);
            for _ in 0..len {
                self.bit_reorganization();
                keystream.push(self.f() ^ self.brc_x[3]);
                self.lfsr_with_work_mode();
            }
            keystream
        }
    }

    const BASE64_CHARS: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    fn to_base64(input: &[u8]) -> String {
        let mut result = String::new();
        let mut i = 0;
        while i < input.len() {
            let b1 = input[i];
            result.push(BASE64_CHARS[((b1 >> 2) & 0x3f) as usize] as char);

            if i + 1 < input.len() {
                let b2 = input[i + 1];
                result
                    .push(BASE64_CHARS[(((b1 & 0x03) << 4) | ((b2 >> 4) & 0x0f)) as usize] as char);

                if i + 2 < input.len() {
                    let b3 = input[i + 2];
                    result.push(
                        BASE64_CHARS[(((b2 & 0x0f) << 2) | ((b3 >> 6) & 0x03)) as usize] as char,
                    );
                    result.push(BASE64_CHARS[(b3 & 0x3f) as usize] as char);
                } else {
                    result.push(BASE64_CHARS[((b2 & 0x0f) << 2) as usize] as char);
                    result.push('=');
                }
            } else {
                result.push(BASE64_CHARS[((b1 & 0x03) << 4) as usize] as char);
                result.push('=');
                result.push('=');
            }
            i += 3;
        }
        result
    }

    let key = [0u8; 16];
    let iv = [1u8; 16];
    let mut state = ZucState::new();

    // Initialization
    state.initialization(&key, &iv);

    // PKCS7 padding
    let mut data = input.as_bytes().to_vec();
    let padding_len = 4 - (data.len() % 4);
    data.extend(vec![padding_len as u8; padding_len]);

    // Generate keystream and encrypt
    let keystream = state.generate_keystream(data.len() / 4);
    let mut result = Vec::new();

    for (i, chunk) in data.chunks(4).enumerate() {
        let mut block = [0u8; 4];
        block.copy_from_slice(chunk);
        let block_u32 = u32::from_be_bytes(block);
        let encrypted = block_u32 ^ keystream[i];
        result.extend_from_slice(&encrypted.to_be_bytes());
    }

    to_base64(&result)
}
